1. Technical Field
The present invention relates to a manufacturing method of a structure body according to a friction stir joining method and, for example, the present invention is suitable for a joining of hollow extruded frame members.
2. Prior Art
A friction stir joining method is a method in which by rotating a round rod (it is called as a rotary tool) which is inserted to a joining portion and moving it along to the joining line, the joining portion is exothermic heated and is softened and solid state fludized and a solid state joining is carried out. The rotary tool comprises a small diameter portion for inserting to the inserting portion and a large diameter portion which positions at an outside. The small diameter portion and the large diameter portion of the rotary tool have the same axis. A boundary between the small diameter portion and the large diameter portion of the rotary tool is inserted slightly to the joining portion. The rotary tool is inclined toward a rear portion against an advancing direction of the joining.
In the friction stir joining, since the rotary tool is inserted to a metal, a large axial insertion force is necessary. In a joining of a hollow extruded frame member, supporting a plate which is orthogonal to a face plate of the hollow extruded frame member is provided integrally and then a bending of the plate according to the insertion force of the friction stir joining can be prevented.
The above stated technique is disclosed in Japanese application patent laid-open publication No. Hei 09-309164 (EP 0797043 A2).
Since friction stir joining is carried out by inserting compulsively the rotary tool to the members to be subjected to the joining, it is necessary to employ a large insertion force. For this reason, it is necessary to burden bearing members of the rotary tool to the large axial insertion force and this invites a high cost in the manufacture of the apparatus.
Further, when the member to be subjected to the joining is a hollow extruded frame member, the inconvenience such face plate bends by the insertion force causes. To prevent this, it is necessary to form thick a thickness of a support plate of the face plate. For this reason, a weight of the hollow extruded frame member becomes large and a weight of the structure body in which the hollow extruded frame members are joined becomes large.
Further, since the two members to be subjected to the joining are combined simply by a temporary fixing welding, according to the insertion of the rotary tool there is an afraid that the temporary fixing welding may be cut down. When the cut down of the temporary fixing welding an interval between the two members to be subjected to the joining changes accordingly it is impossible to carry out a suitable joining.
When the insertion force of the rotary tool is searched, such an insertion force is large during the insertion initial time. When the friction stir joining becomes to an ordinary condition, the insertion force becomes small. This is considered that the immediately after the joining initial time a raise in temperature of the member to be subjected to the joining is not generated.